Sonar image converter

ABSTRACT

A sonar system is disclosed as having a rotatable shaft with an electroacoustical transducer array mounted on one end thereof, a light output diode readout array mounted on the other end thereof, a receiver mounted on said shaft and connected between said transducer and readout arrays. A transmitter is also connected to said electroacoustical array. An electric motor rotates said shaft through a pair of gears, and a programmed function generator causes sonar target search and echo signals to be timely broadcast by said transmitter and received by said receiver during the rotation of said arrays. An objective lens views the outputs from the light diode output array and transmits it via a bundle of optical fibers to a pair of readout prisms located in a diver&#39;&#39;s face mask. With the exception of a large portion of the optical fibers and readout prisms, the entire sonar system may be encased in a waterproof housing to facilitate its being used as a visual aid to underwater swimmers and divers working in turbid water.

tates Patent [191 1 SONAR IMAGE CONVERTER Albert L. Rolle, Lynn Haven,Fla.

[73] Assignee: The United States of America as represented by theSecretary of the Navy, Washington, DC.

22 Filed: Oct. 4,1972

[21] Appl. No.: 296,500

[75] Inventor:

Primary Examiner-Richard A. Farley AtIorizey- Ricliard S Sciascia Don D.oai 'amf Harvey A. David 1 1 Jan.8, 1974 ABSTRACT A sonar system isdisclosed as having a rotatable shaft with an electroacousticaltransducer array mounted on one end thereof, a light output diodereadout array mounted on the other end thereof, a receiver mounted onsaid shaft and connected between said transducer and readout arrays. Atransmitter is also connected to said electroacoustical array. Anelectric motor rotates said shaft through a pair of gears, and aprogrammed function generator causes sonar target search and echosignals to be timely broadcast by said transmitter and received by saidreceiver during the rotation of said arrays. An objective lens views theoutputs from the light diode output array and transmits it via a bundleof optical fibers to a pair of readout prisms located in a divers facemask. With the exception of a large portion of the optical fibers andreadout prisms, the entire sonar system may be encased in a waterproofhousing to facilitate its being used as a visual aid to underwaterswimmers and divers working in turbid water.

17 Claims, 8 Drawing Figures PATENTEUJAH 8 I974 sum 10? 2 SONAR IMAGECONVERTER STATEMENT OF GOVERNMENT INTEREST The invention describedherein may be manufactured and used by or for the Government of theUnited States of America for governmental purposes without the paymentof any royalties thereon or therefor.

FIELD OF THE INVENTION In general, the present invention relates toechosearch-ranging systems, and, in particular, it is a sonar systemthat may be carried by a swimmer-diver to facilitate finding his way andfor locating objects within water, even though said water may besomewhat turbid.

DESCRIPTION OF THE PRIOR ART Heretofore, numerous sonar, radar, andother echosearch-ranging systems have beem employed as a means forfacilitating the navigation of vehicles, as well as for locating objectsin their respective environmental mediums. Moreover, various and sundryhand-held sonars have been used by swimmers and divers, in order toeffectively allow them to see what is in front of them, as they movealong under water.

For many practical purposes, the sonars of the prior art have been quitesatisfactory; however, for the purpose of allowing human beings toactually see underwater objects with optimum visual capability, they,for the most part, leave a great deal to be desired. As a matter offact, when observations are made thereby in water, sea water, or otherliquids or fluids that are less than clear, it is ordinarily extremelydifficult, if not impossible, for the swimmer-diver to discern what mostacquired target objects are from the sonar readout only, inasmuch as theimage resolution of such objects is generlly quitepoor. In addition,those sonars of the prior art which do provide object image resolutionto a degree that is useful to a human being are usually exceedinglycomplex, large in size and weight, require massive power supplies, andotherwise constitute an inordinant burden to the underwaterswimmer-diver using them, both physically and economically. As a matterof fact, such burdens have been so great that, for most practicalpurposes, swimmer-divers have not been able to use them withoutvehicular support, thereby restricting their freedom of operation inmany instances.

SUMMARY OF THE INVENTION The subject invention is a new and unique sonarsystem which is uniquely combined with the face mask of a swimmer-diverin such manner that it actually augments the visibility of underwaterobjects to the human eye without interferring to any adverse extent withthe normal vision thereof. Furthermore, the instant inventionincorporates an improved image resolution technique which is implementedby a new combination of structural elements of relatively compact sizethat is easily ported and operated by a human swimmer-diver with verylittle training.

It is, therefore, an object of this invention to provide an improvedecho-search-ranging system.

Another object of this invention is to provide an improved sonar system.

Still another object of this invention is to provide an improved methodand means for augmenting the sight of an underwater swimmer-diver.

A further object of this invention is to provide an improved sonarsystem having an improved picture image readout of an acquiredunderwater object.

A further object of this invention is to provide an improved ultrasonicimage converter.

Still another object of this invention is to provide a high definitionultrasonic sonar system that facilitates the acquiring andidentification of various and sundry target objects within water, seawater, or any other suitable environmental medium, that may be employedas an aid to vehicle navigation and as a visual aid to swimmers anddivers.

Another object of this invention is to provide an improved method andmeans for producing a television type view or readout of objectsacquired at very short ranges say, from 14 inches to about 10 feetwithin a field of view, so as to thereby improve the ability of swimmersand divers to do arms-length work such as, for instance, makinginspections, making repairs, performing rescues, and the like on bothlarge and small objects located within water, even though said water maybe somewhat turbid.

Another object of this invention is to provide a sonar system that hasimproved signal-to-noise characteristics and an ability to resolve aweekly reflecting surface in the vicinity of a strongly reflectingsurface, thereby effecting a more detailed image thereof.

Another object of this invention is to provide a high definition, shortrange, sonar device which will display television-like pictures inside aswimmer's face mask with a sixty degree field of view in front thereof.

Still another object of this invention is to provide an improved methodand means effecting the scanning of sonar beams over a target area andfor effecting the remote but synchronous display thereof.

Another object of this invention is to provide a rugged, reliable,simplified, high resolution, compact sonar system that is easily andeconomically manufactured, maintained, and operated.

Other objects and many of the attendant advantages will be readilyappreciated as the subject invention becomes better understood byreference to the following detailed description, when considered inconjunction with the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWING FIG. 1 is a schematic perspective viewof the unique sonar and face mask readout combination of this invention;

FIG. 2 is a partial cross-sectional view of the transceiver portion ofthe subject invention;

FIG. 3 is a front view of the reversible electroacoustical transducerarray incorporated in the devices of FIGS. 1 and 2;

FIG. 4 is a rear view of the light emitting diode transducer arrayincluded in the devices of FIGS. 1 and 2;

FIG. 5 is a block diagram of one of a plurality of receiver channelsincorporated in the electronic signal processing portion of the devicesof FIGS. 1 and 2;

FIG. 6 is a graphical representation of a typical broadcast or receivingdirectivity pattern produced by the subject invention for any givenfixed focal length;

FIG. 7 is an idealized graphical representation of some of the signalwaveforms emanating from the various and sundry components of the deviceof FIG. 5; and

FIG. 8 is a schematic perspective diagram that illustrates the advancingincremental range gating which is effected during the normal operationof the subject invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT Referring now to FIGS. 1 and 2but, at this time, primarily to FIG. 1, there is shown a sonartransceiver 11 which is receiving sonic energy 12 after it has been reflected from a target 13.

Sonar 11 includes a cylindrical housing 14, which has contained thereinat the front end thereof an ultrasonic lens 15 which is spatiallydisposed from but in front of a transducer array 16 that is made up of apredetermined arrangement of reversible, electroacoustical, transducerswhich are suitable for both broadcasting and receiving acoustical energywithin the ambient subaqueous or other environment in response to thebroadcast and receiving modes of operation of the subject invention,respectively. As may readily be seen, transducer array 16 is mountedupon a rotatable shaft 17 and, thus, is thus rotatable, too, asindicated by arrows 18. Rotatable shaft 17 extends through a canisterlike housing 19 which is, likewise, attached thereto in such manner asto rotate therewith. In this particular embodiment, canister 19 housesthe electronic circuitry of the sonar system constituting thisinvention, the circuitry of which will be discussed more fullysubsequently. Shaft 17 also has mounted thereon a gear 21 which isadapted for being driven by a pinion 22 which, in turn, is mounted on ashaft 23 of a drive motor 24. At the end of shaft 17 opposite thatcontaining the aforementioned electroacoustical transducer array isanother transducer array 25 which, because it is fixedly connectedthereto, is adapted for rotation therewith in accordance with thedirectivity indicated by arrows 26. In this particular instance,transducer 25 is, in fact, a readout type of transducer which includes aplurality of light output diodes that are arranged in a configurationwhich is substantially similar to that of the plurality ofelectroacoustical transducers incorporated in transducer array 16.Spatially disposed from the aforesaid light diode array 25 is anobjective lens 27, with the disposition thereof such that the field ofview of the aforesaid light diode array 25 will be therewithin. Attachedto the other side of objective lens 27 is a bundle of optical fibers 28which has the other end thereof connected to a pair of conventionalcombining prism eye pieces 29 and 31 that are located in the field ofview of a diver (not shown) when he is wearing a face mask 32.

At this time, it would appear to be noteworthy that any suitable opticalfibers such as, for example, glass or plastic fibers may be employedwhich will transmit light energy from objective lens 27 to both eyepieces 29 and 31. However, it has been determined, that a bundle of150,000 optical fibers is eminently satisfactory for such purpose.Moreover, it should be understood, that the optical fibers employed areconnected in such manner that both eye pieces 29 and 31 receive thevisual view received by the aforementioned objective lens 27.

Although, in this particular instance, a swimmerdivers face shield 32 isshown as being the support means for combining prisms eye pieces 29 and31, it should be understood that any other suitable support means, suchas, for instance, a helmet, goggles, a console readout, or the like, maybe substituted therefor without violating the spirit and scope of thisinvention. Obviously, it would be well within the purview of one skilledin the art having the benefit of the teachings presented herewith toselect whatever readout means would optimize the use of the subjectinvention during any given operational circumstances. Hence, face mask32 is shown as an example only and, thus, should not be considered asconstituting a limitation on the subject invention.

The aforementioned sonar transceiver portion 11 of the invention isshown in much greater detail from a structural standpoint in FIG. 2.Generally speaking, the components referenced with respect to FIG. 1have, likewise, been referenced by similar reference numerals,respectively, in the view thereof presented in FIG.

2, insofar as they are shown therein.

In this particular embodiment, lens 15 is shown as being a compound,temperature-compensated, liquid filled lens of the type specificallydisclosed and claimed in patent application Ser. No. 241,602, entitledAcoustic Lens, by Albert L. Rolle, filed in the U. S. Pat. Office onApr. 6, 1972. Of course, although the instantly disclosed lens may beconsidered as being a preferred embodiment of the type of lens that isused in the subject invention, it should be understood that lens 15 isnot intended to be limited thereto. Accordingly, any other suitable lensmay be substituted therefor, provided it performs the focusing functionsnecessary to the optimum operation of the subject invention.

In this particular embodiment, lens 15 is shown as being mounted on theopen front end of housing 14 in such manner that light energy passingtherethrough will be focused on the array of transducers 16 mounted onshaft 17.

In this particular embodiment, and as thus seen in FIG. 2, an end plate41 is mounted within the front end of housing 14 by means of screws 42.For the purpose of waterproofing the connection between end plate 41 andhousing 42, end plate 41 contains a groove 43 with an O-ring 44 insertedtherein in such manner that it is urged against the inside surface ofsaid cylindrical housing 14. For the purpose of reducing internalacoustical reflections, an anechoic substance 45 of any conventionaltype is mounted on the front surface of end plate 41 as by glueing or insuch other manner as will cause it to adhere thereto. At the center ofend plate 41 is an aperture 46 containing bearings 47 within which theaforementioned shaft 17 is mounted for rotation. An inner groove 48 isalso disposed around the periphery of aperture 46, and an O-ring 49 isinserted therein and against shaft 17 in such manner that a watertightseal is provided thereat, even though a shaft 17 rotates thereagainst.

For purpose of ease of assembly and disassembly of the subject sonar,shaft 17 is actually made in sections with a center section 51telescopically mounted on the front portion 52 thereof and iseffectively connected thereto by means of set screws 53. In abutmentwith the front end of shaft section 51 and surrounding shaft section 52is a forward thrust bearing 54 which is in abutment with theaforementioned bearing 47 and held in place on section 52 of shaft 17 bymeans of set screw 56. Mounted on thrust bearing 54 is an electricalshield disc 57, with said shield disc 57 being mounted thereon in suchmanner as to turn therewith.

Section 51 of shaft 17 extends rearwardly out of cylinder l9 and istelescopically mounted on a rearward section 60 of shaft 17 as by meansof set screws 61. Rear thrust bearing 62 is likewise mounted on shaftsection 60, as by set screw 63, so as to be connected for rotationtherewith. A rear end plate 64 is also mounted within cylindricalhousing 14 and is held in place by a plurality of beam-like braces 66.Of course, braces 66 connect to front end plate 41 by means of screws67, and they are connected to said rear end plate 65 as by means ofscrews 68.

At this time, it might be well to note that forward end plate 41 andrearward end plate 64 have substantially spider-like configurations,when looking at the ends thereof. However, it should be understood thatany other suitable configuration will be acceptable, as far as thespirit and scope of this invention is concerned.

Mounted on rear end thrust bushing 62 is another wire shield electricaldisc 6? which, of course, is attached thereto as by press fit or anyother conventional manner, so as to rotate therewith.

Mounted on rear section 60 of shaft 17 in any conventional manner forrotation therewith is the aforementioned driven gear 21 which, ofcourse, is driven by drive gear 22 connected by means of shaft 23 to theaforesaid drive motor 24, as discussed previously in conjunction withthe discussion of the device of FIG. 1. Also mounted on rear section 60of shaft 17 is an armature 71 which is connected electrically throughsuitable holes within rear section 60 and center section 51 of shaft 17to the various and sundry electronic components located within rotatingcylinder 1? for the powering and driving thereof. Because sucharrangement is conventional in transferring electrical energy torotating parts, such electrical connections have not been specificallydisclosed in FIG. 2. Nevertheless, it would obviously be well within thepurview of one skilled in the art having the benefit of the teachingspresented herewith to effect such electrical connections as arenecessary for the proper operation of all electric and electroniccomponents incorporated in the instant invention. Hence, for the purposeof simplifying this disclosure, said detailed power supplying and otherelectrical lines and wires have been omitted.

Mounted within cylindrical housing 14 by means of brackets 73 or thelike, is a plurality of slip-rings 74 which are in slidable engagementwith the aforementioned armature 71 as necessary to supply electricalenergy to the respective components thereof.

At the rear extremity of rear section 60 of shaft 17 is mounted theaforementioned light emitting diode array 25. Of course, said array maybe connected to rear shaft section 60 in any conventional manner, suchas by set screws 75 or the like, and furthermore, the individual lightdiodes of light emitting diode transducer array 25 are electricallyconnected by means of electrical wires or leads through the hollows ofrear section 60 and center section 51 and suitable apertures locatedtherein (not shown) to the various and sundry electronic componentsassociated therewith and located within the aforementioned rotatingcylinder 19, as will be disclosed and discussed in some greater detailsubsequently in conjunction with the discussion of FIG. 5.

At the rear extremity of cylindrical housing 14 is an end plate 77 whichis connected thereto as by means of screws 78. To provide watertightsealing between set-in plate 77 and the inside surface of housing 14 anO-ring 79 is located in a groove 81 disposed around the periphery of endplate 77. Of course, the resilient urging of O-ring 79 against end plate77 and housing 14 affects said watertight seal therebetween.

Located within an aperture 82 located in the center of rear end plate 77and in alignment with the center of the aforementioned light emittingdiode array 25 is the aforesaid bundle of fiber optics 28. Of course, aspreviously indicated on the front end of said bundle of fiber optics 28is an objective lens 27 which has a field of view defined by imaginarycone 83 which, as may readily be seen, is broadened at the base thereofto sufficiently encompass the entire rear face of light emitting diodetransducer array 25. Because optical fibers 28 extend through rear wall77, a watertight seal must be provided therebetween. Accordingly, asuitable packing gland 84 is inserted therebetween in any conventionalmanner.

Another packing gland 86 is inserted within hole 87 likewise locatedthrough the wall of rear end plate 77 for providing a watertight sealtherebetween and, yet, allow the passage of electrical wire or leadstherethrough in such manner that they may be connected to theaforementioned drive motor 24 and slip-ring 74 for supplying electricalpower thereto, respectively, from some externally located electricalpower supply and controls therefor probably located in the back pack ofa diver (likewise not shown).

At this time, it would appear to be noteworthy to mention that the sonardevice located within cylindrical housing 14 may be of any size that isnecessary to perform the operations desired. Therefore, it may be ofsuch external dimension as would allow it to be held by the hand of aswimmer-diver who is probing the water or sea water which is turbid orin such condition otherwise as would require a visual aid in order forsaid diver to navigate and perform any work which he wants to do. On theother hand, it may also be of such dimension as would facilitate itbeing mounted on any suitable underwater vehicle or, for that matter, onany other type of device located in any appropriate environmental mediumwithin which sonar-like operations can be used to an advantage. Again,it would obviously be well within the purview of the artisan to designthe subject invention in its entirety in such manner that it may be usedin conjunction with a human being or manned or unmanned vehicles or thelike for any suitable purpose within water, air, space, or any otherappropriate environmental medium.

Referring now to FIG. 3, there is shown a front view of theelectroacoustical transducer array previously designated in FIGS. 1 and2 as transducer array 16. In this particular instance, transducer array16 is shown schematically as having a predetermined geometricalconfiguration of individual electroacoustical transducer elements 91.Although the pattern shown in FIG. 3 is found to be optimum, it shouldbe understood that any other pattern of transducer elements 91 may beemployed if warranted by operational circumstances.

FIG. 4 discloses a rear view of the aforementioned light emitting diodetransmitter array 25 as including a plurality of light emitting diodes92 arranged in a pattern which corresponds, respectively, to theircounter parts, that is, to electroacoustical transducer elements 91 intransducer array 16 of FIG. 3. Again, like the array pattern of FIG. 3,the array pattern of light emitting diodes 92 may be such as wouldoptimize the operation of the entire invention during any givencircumstances. However, as a general rule, the pattern of light emittingdiodes 92 will be similar to the pattern of electroacoustical transducerelements 91, inasmuch as such an arrangement appears to optimize thetransfer of energy therebetween and between their respective associatedobjects or elements.

Referring now to FIG. 5, there is shown the aforementioned transducerarray 116 as including an electroacoustical transducer 91 as one of thecomponents thereof. The output of transducer 91 in this particularinstance constitutes one of the outputs of transducer array 16 and isconnected to the input-output of one of transmit-receiver (TR) switches93. Another of the inputs of transmit-receive switches 93 is connectedto the output of a transmitter 94, and one of the outputs oftransmit-receive switches 93 is connected to the input, in thisparticular example, of one of the receiver channels 95 of apredetermined number of receiver channels, the number of which isdetermined by the number of electroacoustical transducer elementslocated in transducer array 16 and the number of light output diodeslocated in diode array 25. Because all of the receiver channels aresubstantially identical, only one thereof is shown herewith, in order tokeep this disclosure as simple as possible.

At this time, it would perhaps be noteworthy that the aforementionedtransducer 91, TR switch 93, transmitter 94, and receiver channel 95 arecombined in the conventional manner, so as to prevent cross-talk fromoccurring between the transmitter and receivers that is, so as toprevent reception from occurring during the mode of transmission and toprevent transmission from occurring during the mode of reception.

The input to receiver channel 95 is, in this case, the data signal inputto an analog gate 96. The output of analog gate 96 is connected to theinput of a variable gain preamplifier 97, the output of which isconnected to the input of a tuned time-varied-gain amplifier 98. Theoutput of tuned time-varied-gain amplifier 9? is connected through adetector 99 to the data signal input of a peak detector and memorycircuit NH. The output of peak detector and memory circuit lltlill isconnected to the input of a circuit isolation emitterfollower 102, theoutput of which is connected to the input of light output diode 92 ofdiode transducer array 25. The aforementioned analog gate 96 has a rangegate pulse input, the aforementioned tuned timevaried-gain amplifier 98has a gain control voltage input, and peak detector and memory circuitHill has a reset pulse input, all of which are respectively connected toone of the range gate outputs, one of the gain control voltage outputs,and one of the reset pulse outputs ofa function generator 103. Likewise,transmitter 94 is connected to transmit pulse output of functiongenerator 103.

Because there is usually several pluralities of receiver channelsincluded in the operational design of the subject sonar, anotherplurality of receiver channels MM is disclosed. Also. in such case,another plurality of trans mit-receive switches 105 is shown as beingconventionally connectcd to receiver channels 104, transmitter 94, andtransducer array 16. A multiplexer I06 is, moreover, connected betweenthe programmer output of the aforesaid function generator 103 and thegating inputs of receiver channels 104 for the timely activationthereof. Hence, one or more of the receiver channels of this inventionmay be operative at any given instant.

At this time, it would perhaps be noteworthy that all of the elementsdisclosed in FIG. 5 are Well known conventional, and commerciallyavailable, per se, and, hence, it should be understood that it is theirunique interconnections and interactions which consititute new andimproved receiver channel portions of the subject invention and whichmake an important contribution to the improved operation producedthereby.

FIGS. 6, 7, and 8 are not structural in nature and, thus, will not bediscussed in detail at this time; however, they will be discussed duringthe discussion of the mode of operation which follows.

MODE OF OPERATION The operation of the subject invention will now bediscussed briefly in conjunction with all of the figures of the drawing.

The high definition sonar constituting this invention is actually anultrasonic image converter which displays a television-like pictureinside the face mask of a predetermined viewing sector locatedimmediately in front of the diver wearing the face mask. As the divertravels along his underwater course, he causes the subject sonar systemto broadcast sonic energy throughout the ambient environment medium inaccordance with a radiation pattern which is typically shown in FIG. 6.Such broadcast, of course, is actually implemented by transmitter 94energizing all of the transducer elements of transducer array 16 beingrotated as a result of motor 24 effectively during shaft 17 throughshaft 23, drive gear 22, and driven gear 21. In effect, such rotation oftransducer array 16 effects the acquiring of target 13 with a pluralityof sonar beams which are reflected therefrom back to transducer array 16for reception thereof during the received mode of operation of thesonar. Again, rotating transducer array 16 during the received mode ofoperation effects the scanning of the aforesaid plurality of sonar beamsover the target area and, thus, receives those which are reflected backfrom the target as a high definition image thereof.

As a general rule, the fundamental problem in finding high definitionsonar images is the occurrence of low level returns from a large portionof a targets surface. Even at relatively high operating frequencies,such reflections from typical surfaces are predominantly specular innature. Therefore, from a large portion of the target surface, the echolevel may be inadequate for processing because the majority of the soundenergy may have been reflected away from the receiver, rather thandirectly toward it. When the specular component of said echo signal isin the direction of the receiver, the echo level is, of course, veryhigh. It has been found that the range between the low-level and thehigh-level echoes from a typical target surface may theoretically be asgreat as db. Consequently, as may readily be seen, the target resolutioncan be improved considerably if the echoes therefrom can be effectivelyconcentrated at its reception point. For this reason, in order tooperate effectively with specularly reflecting surfaces, the subjectsonar system uses the same transducer elements to both project andreceive the broadcast and target reflected sonic energy. For purposes ofoptimization, the plurality of electroacoustical trans ducer elementsshould be'spaced in such manner that adjacent beams that are activatedduring a particular pulse overlap at the minus 50 db points of thecomposite patterns. As a result of so doing, higher source levels can beobtained, compared to a broad beamed insonifler with the same power,thereby effectively increasing the proportion of a targets surface fromwhich the received echoes will be above the noise, and, hence, improvingthe signal-to-noise ratio. Also, the greater isolation acquired betweenthe sonar beams of theinstant invention improves its ability to resolvea weekly reflecting surface signal in the vicinity of a stronglyreflecting surface signal and, thus, forms a more detailed image.

During the transmission mode of operation, the transducer elementsshould be driven at the maximum peak power level, in order to increasethe proportion of a targets surface from which the echo is above thenoise. In this particular case, in order to deal effectively with thetarget return signals from those portions of the target that reflect thespecular component directly toward the receiver, the transducer arrayand all of the post transducer electronic circuitry associated therewithshould be designed to preserve as high a db isolation attainment aspossible between sonar beams. Insonifying a total target area, as ageneral rule, compounds the specularity problem because every resolvablepoint of target surface contributes to the apparent pressure amplitudeat the receiver; however, by insonifying only a small fraction of thetarget surface at any given instant in the manner effected by thisinvention causes the possible number of interferring reflectors to bereduced considerably.

A very important factor in causing the instant device to produce a highdefinition target image is the fact that both the electroacousticaltransducer array and the light output diode array are synchronouslyrotated at such a speed as to cause the beam of the transducer elementsfurtherest from the axis of rotation to move to no more than one beamwidth of the one-way pattern in a period corresponding to the two-waypulse travel time for the longest range. Therefore, it may readily beseen that particular target range corresponds to a particular rotationalrpm,-and because the array is symmetrical about the center of rotation,two complete pictures are formed for each revolution. Thus, by selectingthe proper rotation speed, the frame rate may be made sufficiently highto prevent undue flicker in the display.

Because the elements of the electroacoustical transducer array nearerthe axis of rotation are moved through a smaller arc than the outerelements for the same angular displacement, the outputs of these innerelements during the receiving mode of operation are preferablemultiplexed to reduce the number of required signal processing channelsrequired. As would be obvious to the artisan having the benefit of theteachings presented herewith, such multiplexing could be effected bycausing the outer elements of transducer array 16 to be sensedcontinuously, with half of the intermediate elements thereof sensed withevery projected pulse, and with only one-third of the innerelementsthereof sampled every' transmitted pulse. By using such arrangement, alesser number of channels is required for any given number of individualtransducer elements located within the broadcasting and receivingtransducer array 16. Consequently, depending upon the multiplexingarrangement selected, the number of channels employed in the instantinvention becomes a matter of design choice, the making of which wouldbe well within the purview of one skilled in the art.

As may readily be seen from FIG. 2, the degree of concentration oftarget echoes received by a transducer array 16 is contingent upon thefocusing power of acoustic lens 15 disposed in front thereof. Althoughthe aforementioned lens 15 is herewith disclosed as being a particularliquid acoustic lens believed to be of patentable significance in itsown right, it should be understood that other liquid or solid acousticlenses may be substituted therefor, so long as they properly accom plishthe desired acoustic energy focusing effect upon transducer array 16.

During the receiving mode of operation, the received echo signals froman acquired target will be processed in all of the receiver channels inthe same manner. Therefore, in order to keep this disclosure as simpleas possible, the processing thereof through only one channel, namelyreceiver channel 95, will be discussed in detail herewith. In thisparticular case, the X and Y coordinants of the light output diode arraydisplay enhance in the display within eye pieces 29 and 31 and representa bearing and inclination, respectively, rather than bearing and range,as is found in the more conventional sonars. Because of thetime-varied-gain employed to increase the receivers dynamic range andthe specular nature of the reflected sound, range is not directlydiscernible from the display. Hence, the signal processing of theinstant invention is based on the premise that, from a particulardirection, the signal of major interest is the highest level echo. Apeak detector and memory circuit at the output of the envelope detectoris therefore employed to store the level of the strongest echo for aperiod of time that is inversely proportional to the range of the targetor for some minimum time, as desired. This pulse-stretching processincreases the average display intensity and allows direct viewing of thelight output diode display with short projected or transmitted pulses.

Variable-width range gating is provided by analog gate 96 (which is,electrically speaking, located prior to preamplifier 97) and tunedtime-varied-gain amplifier 98. The objective of the range gating is toprovide some indication of target range and to attain a shadowgraph"effect for difficult target-background situations. For example, byautomatically stepping in range as shown in some detail in FIG. 8, asmall target object attached to a larger target object may first appearas a bright spot on a dark background and then as a dark spot on abrighter background, as the gate moves out in range. This effect, whenproperly employed, will increase the probability of detection andclassification of objects or target features that may ordinarily tend toblend into their ambient background.

A rotating receiving array was selected because of its simplicity, lowcomponent count, and large area available for spacing the elements forincreased acoustic isolation between beams. The rotating light outputdiode array as a type of display is employed because it is compatiblewith the rotational scanning of the electroacoustical transducerreceiving array. The major advantages of the two rotating arrays arethat they display scanning electronics and the related multiplexing ofthe envelope detector outputs, they eliminate multiple high voltages anddc to dc converters, and they provide a pulsed high intensity output fora small power drive per light output diode in the diode array. Inaddition, the

display volume is less than one-tenth of that which would be requiredif, for example, a cathode-ray tube were used as the readout and,moreover, the reliability and operating life are increasedsignificantly.

On the other hand in the event it is found to be objectionable to havesome flicker in the display of the subject invention, it may besubstantially eliminated or at least reduced by optionally placing animage intensifier tube between the light output diode array and theobserver. With a phosphor of the proper persistency and an acceleratingpotential high enough, the light output should be comparable to anapplicable miniature cathode ray tube. Such apparatus has beendemonstrated to suppress flicker sufficiently to enable the overallsonar system to perform adequately in those situations in which flickercannot be tolerated. However, in most instances, the amount of flickerinvolved during the normal operation of the diode array embodiment wouldbe negligible.

As a general rule, a swimmers forward speed is typically less thanone-half knot or about ten inches per second. For this speed, the targetimage quality and fidelity is adequate for most practical purposes. As amatter of fact, it provides a considerable visual aid to the diver notobtainable by any other known method or means without any inconveniencethereto.

In the foregoing, a general discussion was presented relative to theoverall operation of the subject invention. Now, in order to moreclearly explain the internal operations of the electronic portion of theinvention. the device of FIG. will be discussed in conjunction with thesignal wave forms presented in FIG. 7. Again, it should be understood,that FIG. 5 only presents a sin gle channel portion ofa multichannelsystem constituting this invention, the channels of which may bemultiplexed as mentioned previously.

In accordance with a gating signal of the type comparable to that shownin FIG. 7A, transmitter 94- is turned on and causes transducer 91 tobroadcast a CW type pulse signal similar to that shown in FIG. 78. Ofcourse, said broadcast CW pulse is actually a search signal which uponimpact with an underwater target is reflected therefrom as an echosignal. In accordance with the program set forth in the functiongenerator range gate pulses of the type depicted in FIG. 7C timely opennormally closed analog gate 96, so as to allow the aforesaid target echosignals to pass therethrough in the event the target from which they arereflected have a range which coincides with the range programmed at thatparticular instant by the range gate pulse from function generator 103.As shown in FIG. 8, of course, the subject sonar system has a totalrange capability; however, because range gating is employed therein,various and sundry range segments depicted as the segments locatedbetween the distances AR in FIG. 8 target objects are searched at andare indicated as being acquired at a particular range distance. Hence,if the received target echo is supplied to the input of analog gate 96at the time it is opened by the range gate pulse of FIG. 7C, it passestherethrough as being from some particular target range, whereupon it isamplified by preamplifier 97 to a more useful level. In order to thenimprove the fidelity of the target echo signal it is further processedby tuned time-varied-gain amplifier 98 as is conventional in suchamplifiers when a large number of target ranges are encountered. Inorder to effect the proper amplification by tuned time-variedgainamplifier 98, gain control signals of the type exemplarily depicted inFIG. 7D are supplied to the control input thereof. As a result of theaforementioned range gating and time-varied-gain amplification, thetarget echo signals such as that portrayed in FIG. 7E, are passedthrough both thereof at the time that analog gate 96 is open, therebyeliminating all other signals that may be received and clearly producingthe acquired target signals in the manner exemplarily illustrated inFIG. 7F. By comparing the signal waveform of signal FIG. 7E and thesignal of FIG. 7F, it may readily be seen that the aforementionedprocedure substantially deletes all spurious signals for the disclosedparticular range when analog gate 96 is open. When the signal of FIG. 7Fis detected by detector 99, it becomes a signal having a waveformcomparable to that shown in FIG. 7G, and when the peak thereof isdetected and stored in peak detector and memory 101, the resultingsignal becomes similar to that illustrated in FIG. 7H. For circuitisolation purposes, in order to delete as much of the spurious noiseencountered as possible, the output from peak detector memory 101 ispassed through emitter-follower 102 before it is supplied to lightoutput diode 92 in diode array 25 as the signal ideally illustrated inFIG. 7I.

As may readily be seen from inspection of FIGS. 7H and 7], peak detectorand memory 101 are reset by the 'reset pulse supplied to the reset inputthereof from function generator 103 at approximately the time that thenext search signal is broadcast by transmitter 94 and transducer 91.Accordingly, the memory portion of peak detector and memory 101 storesthe signal processed thereby for the period of time between the receivedtarget signal is detected by detector 99 and the next search signal isbroadcast. Of course, the signal of FIG. 7[ is that which is supplied tolight diode 92 which turns it on for the period of time said signal ispositive in polarity.

From the foregoing, it may readily be seen that the broadcast of asearch signal, the reception of a target echo thereof, and theprocessing through a receiver channel causes alight display to occur inthe light diode array. Of course, such signal performance and processing timely occurs in each of the channels in substantially the samemanner as just described in connection with receiver channel of FIG. 5.When all channels are operative, those light output diodes are energizedas light dots on the array display, and the configuration thereof whichis lighted at any given instant functions to effect a picture-like imageof the target acquired.

As previously indicted, the proper multiplexing of receiver channelswill, as a general rule, optimize target image fidelity for any givenoperational circumstances. For example, it has been found that goodresults occur if thirty-one transducers and 22 receiver channels areincorporated in the invention, with multiplexing thereof programmed insuch manner that sixteen transducers perform full time, six transducersperform onehalf of the time, and nine transducers perform onethird ofthe time. Of course, other timing arrangements of the transducer andchannel combinations may be employed, if so desired. Obviously, it wouldbe well within the purview of one skilled in the art having the benefitof the teachings presented herewith to design the multiplexer and itsprogram in such manner as to provide any multiplexing system requiredduring any given operational circumstances.

As may best be seen in FIG. 2, whatever light diode picture-like imageis portrayed by diode array 25 is received by objective lens 27which,j,n.turn, focuses it on the ends of the 180,000 fiber opticbundle, where it is conducted therein to the eye pieces 29 and 31located in mask 32, where it becomes an important visual aid to thediver wearing said mask.

Again, for purposes of emphasis, because it is exceedingly important tothe optimum operation of the subject invention, attention is directed tothe fact that shaft 17, transmitting and receiving electroacousticaltransducer 16, light diode readout array 25, and the sig nal processingelectronics connected therebetween are simultaneously rotated and, thus,rotated in synchronism during the broadcast of target search signals andthe reception of echo signals therefrom. Such operation causes thesubject sonar to produce high fidelity, picture-like, target objectimages not obtainable in any other known way. Of course, such improvedresults occur because, during the broadcast mode, the search signalsscan the acquired target along concentrated small path areas thereon,rather than insonifying the entire target at once. Hence, the echosignals reflected therefrom are likewise'concentrated over a small areaat any given instant, thereby improving the strength and qualitythereof. Moreover, such concentrated scanning search and echo signalstend to stand out against whatever contiguous spurious targetreflections or ambient environmental medium noise signals may be presentin the target area. As a result, when the concentrated scanning thereofis properly processed and synchronously readout or displayed byappropriate transducers, the image of an acquired target is enhancedconsiderably, and is especially valuable for provding a visual aid toswimmers and divers doing work within a turbid subaqueous environment.

From the foregoing it may readily be seen that the subject inventionconstitutes a new and unique combination of well known and conventionalindividual elements which produces results as far as target resolutionis concerned which are vastly improved over those obtained by knownsonar systems and thus, it ostensively constitutes an advancement ofconsiderable significance in the sonar art.

Obviously, other embodiments and modifications of the subject inventionwill readily come to the mind of one skilled in the art having thebenefit of the teachings presented in the foregoing description and thedrawings. It is, therefore, to be understood that this invention is notto be limited thereto and that said modifications andembodiments areintended to be included within the scope of the appended claims.

What is claimed is:

l. A sonar system, comprising in combination:

a rotatable shaft;

a plurality of reversible electroacoustical transducers disposed in anarray having a predetermined pattern mounted on one end of saidrotatable shaft;

a plurality of light output diodes disposed in an array having a patternsubstantially similar to array pattern of the aforesaid plurality ofreversible electroacoustical transducers, respectively, mounted on theother end of said shaft;

means effectively connected to the inputs of said plurality ofreversible electroacoustical transducers for the timely energizationthereof, respectively, mounted on said rotatable shaft;

a receiver means having a plurality of receiving channels with theinputs thereof respectively effectively connected to the outputs ofpredetermined ones of said plurality of reversible electroacousticaltransducers and with the outputs thereof respectively connected to theinputs of predetermined ones of said plurality of light output diodesmounted on said rotatable shaft;

function generator means connected to the aforesaid reversibleelectroacoustical transducer energizing means and said receiver meansfor effecting the broadcasting and receiving of predetermined signalsthereby in accordance with predetermined programs, respectively; and

means connected to said rotatable shaft for effecting the rotationthereof while the aforesaid predetermined signals are being broadcastand received.

2. The device of claim 1, wherein said means effectively connected tothe inputs of said plurality of re versible electroacousticaltransducers for the timely energization thereof, respectively, mountedon said rotatable shaft comprises a transmitter.

3. The device of claim 1 wherein each of the receiving channels of saidreceiving means comprises:

an analog gate having a data signal input effectively connected to oneof the reversible electroacoustical transducers of the aforesaid arraythereof and a control input adapted for the opening thereof in responseto a range gate pulse signal;

a tuned time-varied-gain amplifier having a data signal input and a gaincontrol voltage signal input, with the data signal input thereofeffectively connected to the output of said analog gate;

a detector connected to the output of said tuned time-varied-gainamplifier;

a peak detector and memory having a data signal input and a reset pulseinput, with the data signal input thereof connected to the output ofsaid detector; and

an emitter-follower connected between the output of said peak detectorand memory and one of the aforesaid light output diodes of the arraythereof.

4. The device of claim 1, wherein said means connected to the aforesaidreversible electroacoustical transducer energizing means and saidreceiver means for effecting the broadcasting and receiving of predetermined signals thereby in accordance with predetermined programscomprises a. programmed function generator which timely producestransmitter gating signals, range gate pulses, gain control voltagesignals, and reset pulses.

5. The device of claim 1, wherein said means connected to said rotatableshaft for effecting the rotation thereof while the aforesaidpredetermined signals are being broadcast and received comprises:

a driven gear connected to said rotatable shaft;

a drive gear disposed for driving engagement with said driven gear; and

a motor having a rotatable shaft connected to said dirve gear.

6. The invention of claim 1, further characterized by a plurality oftransmit-receive switches connected between said plurality of reversibleelectroacoustical transducers, said energization means therefor, and theaforesaid receiver means, respectively.

7. The invention of claim 1, further characterized by:

an objective lens spatially disposed from said light output diode arrayin such manner as to have said light output diode array in the field ofview thereof;

a readout; and

means connected between the optical output of said lens and the opticalinput of said readout for transmitting images formed by the former tothe latter.

8. The invention of claim 1, further characterized by:

an objective lens spatially disposed from said light output diode arrayin such manner as to have the light output thereof focused at apredetermined spot thereby;

a pair of combining prism 'eye pieces for presenting visual imagesof-objects; and

a bundle of optical fibers connected between the focal spot of saidobjective lens and the optical inputs of said pair of combining prismeye pieces.

9. The invention of claim 1, further characterized by:

an objective lens spatially disposed from said light output diode arrayin such manner as to have said light output diode array in the field ofview thereof;

a divers face mask;

a pair of combining prism eye pieces respectively mounted within saiddivers face mask in such manner as to be in alignment with and in frontof the eyes of a diver wearing said face mask; and

a bundle of optical fibers connected between the optical output of saidobjective lens and the optical inputs of said pair of combining prismeye pieces.

10. The invention of claim 1, further characterized by a waterproofhousing encasing said sonar system.

11. The invention of claim 1, further characterized by:

another plurality of receiver channels having a plurality of inputs andoutputs, with predetermined ones of the inputs thereof connected topredetermined ones of the outputs of said function generator means, andwith the outputs thereof connected to predetermined ones of saidplurality of light output diodes, respectively; and

a like plurality of transmit-receive switches connected betweenpredetermined ones of said plurality of reversible electroacousticaltransducers, said energization means, and predetermined inputs of theaforesaid plurality of receiver channels, respectively.

12. The invention of claim 11, further characterized by means connectedbetween a predetermined output of said function generator means andpredetermined inputs of said another plurality of receiving channels foreffecting the multiplexing thereof in accordance with a predeterminedprogram.

113. The invention of claim 1, further characterized by an acoustic lensmeans spatially disposed from said plurality of reversibleelectroacoustical transducers in such manner as to be located in theoperative fields of projection and reception of the acoustical energytimely broadcast and received thereby.

14. A sonar system, comprising in combination:

a reversible electroacoustical transducer for broadcasting and receivingacoustical energy in accordance with a predetermined directivitypattern;

a transmitter effectively connected to the output of said reversibleelectroacoustical transducer for the timely energization thereof;

a receiver effectively connected to the output of said reversibleelectroacoustical transducer;

a light output diode connected to the output of said receiver anddisposed in such manner as to shine its light energy in accordance witha predetermined directivity pattern; I

an objective lens spatially disposed from said light output diode insuch manner that the predetermined directivity pattern of the lightenergy therefrom is located within the field of view thereof;

function generator means connected to the aforesaid transmitter andreceiver for timely effecting the transmission and reception thereof inaccordance with predetermined operational programs, respectively; and

means connected to the aforesaid reversible electro acousticaltransducer, to said transmitter, to said receiver, to said functiongenerator means, and to said light output diode for effecting thesimultaneous rotation thereof about a common axis.

15. The invention of claim 14, further characterized by meanseffectively connected to the output of said objective lens forconducting light energy transmitted therethrough to a predeterminedlocation remote therefrom.

16. The invention of claim 15, further characterized by a readoutconnected to the remote output of said light conducting'means fordisplaying the light energy conducted thereby.

17. The invention of claim 14, further characterized by an acoustic lensmeans spatially disposed from said reversible electroacousticaltransducer in such manner as to be located in the operative fields ofprojection and reception of the acoustical energy timely broadcast andreceived thereby.

1. A sonar system, comprising in combination: a rotatable shaft; aplurality of reversible electroacoustical transducers disposed in anarray having a predetermined pattern mounted on one end of saidrotatable shaft; a plurality of light output diodes disposed in an arrayhaving a pattern substantially similar to array pattern of the aforesaidplurality of reversible electroacoustical transducers, respectively,mounted on the other end of said shaft; means effectively connected tothe inputs of said plurality of reversible electroacoustical transducersfor the timely energization thereof, respectively, mounted on saidrotatable shaft; a receiver means having a plurality of receivingchannels with the inputs thereof respectively effectively connected tothe outputs of predetermined ones of said plurality of reversibleelectroacoustical transducers and with the outputs thereof respectivelyconnected to the inputs of predetermined ones of said plurality of lightoutput diodes mounted on said rotatable shaft; function generator meansconnected to the aforesaid reversible electroacoustical transducerenergizing means and said receiver means for effecting the broadcastingand receiving of predetermined signals thereby in accordance withpredetermined programs, respectively; and means connected to saidrotatable shaft for effecting the rotation thereof while the aforesaidpredetermined signals are being broadcast and received.
 2. The device ofclaim 1, wherein said means effectively connected to the inputs of saidplurality of reversible electroacoustical transducers for the timelyenergization thereof, respectively, mounted on said rotatable shaftcomprises a transmitter.
 3. The device of claim 1 wherein each of thereceiving channels of said receiving means comprises: an analog gatehaving a data signal input effectively connected to one of thereversible electroacoustical transducers of the aforesaid array thereofand a control input adapted for the opening thereof in response to arange gate pulse signal; a tuned time-varied-gain amplifier having adata signal Input and a gain control voltage signal input, with the datasignal input thereof effectively connected to the output of said analoggate; a detector connected to the output of said tuned time-varied-gainamplifier; a peak detector and memory having a data signal input and areset pulse input, with the data signal input thereof connected to theoutput of said detector; and an emitter-follower connected between theoutput of said peak detector and memory and one of the aforesaid lightoutput diodes of the array thereof.
 4. The device of claim 1, whereinsaid means connected to the aforesaid reversible electroacousticaltransducer energizing means and said receiver means for effecting thebroadcasting and receiving of predetermined signals thereby inaccordance with predetermined programs comprises a programmed functiongenerator which timely produces transmitter gating signals, range gatepulses, gain control voltage signals, and reset pulses.
 5. The device ofclaim 1, wherein said means connected to said rotatable shaft foreffecting the rotation thereof while the aforesaid predetermined signalsare being broadcast and received comprises: a driven gear connected tosaid rotatable shaft; a drive gear disposed for driving engagement withsaid driven gear; and a motor having a rotatable shaft connected to saiddirve gear.
 6. The invention of claim 1, further characterized by aplurality of transmit-receive switches connected between said pluralityof reversible electroacoustical transducers, said energization meanstherefor, and the aforesaid receiver means, respectively.
 7. Theinvention of claim 1, further characterized by: an objective lensspatially disposed from said light output diode array in such manner asto have said light output diode array in the field of view thereof; areadout; and means connected between the optical output of said lens andthe optical input of said readout for transmitting images formed by theformer to the latter.
 8. The invention of claim 1, further characterizedby: an objective lens spatially disposed from said light output diodearray in such manner as to have the light output thereof focused at apredetermined spot thereby; a pair of combining prism eye pieces forpresenting visual images of objects; and a bundle of optical fibersconnected between the focal spot of said objective lens and the opticalinputs of said pair of combining prism eye pieces.
 9. The invention ofclaim 1, further characterized by: an objective lens spatially disposedfrom said light output diode array in such manner as to have said lightoutput diode array in the field of view thereof; a diver''s face mask; apair of combining prism eye pieces respectively mounted within saiddiver''s face mask in such manner as to be in alignment with and infront of the eyes of a diver wearing said face mask; and a bundle ofoptical fibers connected between the optical output of said objectivelens and the optical inputs of said pair of combining prism eye pieces.10. The invention of claim 1, further characterized by a waterproofhousing encasing said sonar system.
 11. The invention of claim 1,further characterized by: another plurality of receiver channels havinga plurality of inputs and outputs, with predetermined ones of the inputsthereof connected to predetermined ones of the outputs of said functiongenerator means, and with the outputs thereof connected to predeterminedones of said plurality of light output diodes, respectively; and a likeplurality of transmit-receive switches connected between predeterminedones of said plurality of reversible electroacoustical transducers, saidenergization means, and predetermined inputs of the aforesaid pluralityof receiver channels, respectively.
 12. The invention of claim 11,further characterized by means connected between a predetermined outputof said function generator means and predetermined inputs of saidAnother plurality of receiving channels for effecting the multiplexingthereof in accordance with a predetermined program.
 13. The invention ofclaim 1, further characterized by an acoustic lens means spatiallydisposed from said plurality of reversible electroacoustical transducersin such manner as to be located in the operative fields of projectionand reception of the acoustical energy timely broadcast and receivedthereby.
 14. A sonar system, comprising in combination: a reversibleelectroacoustical transducer for broadcasting and receiving acousticalenergy in accordance with a predetermined directivity pattern; atransmitter effectively connected to the output of said reversibleelectroacoustical transducer for the timely energization thereof; areceiver effectively connected to the output of said reversibleelectroacoustical transducer; a light output diode connected to theoutput of said receiver and disposed in such manner as to shine itslight energy in accordance with a predetermined directivity pattern; anobjective lens spatially disposed from said light output diode in suchmanner that the predetermined directivity pattern of the light energytherefrom is located within the field of view thereof; functiongenerator means connected to the aforesaid transmitter and receiver fortimely effecting the transmission and reception thereof in accordancewith predetermined operational programs, respectively; and meansconnected to the aforesaid reversible electroacoustical transducer, tosaid transmitter, to said receiver, to said function generator means,and to said light output diode for effecting the simultaneous rotationthereof about a common axis.
 15. The invention of claim 14, furthercharacterized by means effectively connected to the output of saidobjective lens for conducting light energy transmitted therethrough to apredetermined location remote therefrom.
 16. The invention of claim 15,further characterized by a readout connected to the remote output ofsaid light conducting means for displaying the light energy conductedthereby.
 17. The invention of claim 14, further characterized by anacoustic lens means spatially disposed from said reversibleelectroacoustical transducer in such manner as to be located in theoperative fields of projection and reception of the acoustical energytimely broadcast and received thereby.